[PATCH v7] ld: Make archive member file extension comparisons case insensitive when cross compiling too

["Martin Storsjö" <martin@martin.st>]

On Windows, filename_cmp is case insensitive, but when cross compiling
with libraries that may contain members with uppercase file names, we
should keep those comparisons case insensitive when running the build
tools on other OSes too.

Also make the check for .def consistent with the other ones, fixing
out of bounds reads if file names are shorter than 4 characters.
---
v7: Skip the '.' entirely in the first parameter to fileext_cmp too,
simplifying the function and making the two parameters more symmetrical.
---
 ld/emultempl/pe.em  | 27 ++++++++++++++++++++++-----
 ld/emultempl/pep.em | 27 ++++++++++++++++++++++-----
 2 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/ld/emultempl/pe.em b/ld/emultempl/pe.em
index ad969ccec13..2706d73d144 100644
--- a/ld/emultempl/pe.em
+++ b/ld/emultempl/pe.em
@@ -534,6 +534,23 @@ gld${EMULATION_NAME}_list_options (FILE *file)
   fprintf (file, _("  --build-id[=STYLE]                 Generate build ID\n"));
 }
 
+/* A case insensitive comparison, regardless of the host platform, used for
+   comparing file extensions.  */
+static int
+fileext_cmp (const char *s1, const char *s2)
+{
+  for (;;)
+    {
+      int c1 = TOLOWER (*s1++);
+      int c2 = *s2++; /* Assumed to be lower case from the caller.  */
+
+      if (c1 != c2)
+        return (c1 - c2);
+
+      if (c1 == '\0')
+        return 0;
+    }
+}
 
 static void
 set_pe_name (char *name, long val)
@@ -1666,7 +1683,7 @@ gld${EMULATION_NAME}_after_open (void)
 		       extension, and use that for the remainder of the
 		       comparisons.  */
 		    pnt = strrchr (bfd_get_filename (is3->the_bfd), '.');
-		    if (pnt != NULL && filename_cmp (pnt, ".dll") == 0)
+		    if (pnt != NULL && fileext_cmp (pnt + 1, "dll") == 0)
 		      break;
 		  }
 
@@ -1683,7 +1700,7 @@ gld${EMULATION_NAME}_after_open (void)
 			/* Skip static members, ie anything with a .obj
 			   extension.  */
 			pnt = strrchr (bfd_get_filename (is2->the_bfd), '.');
-			if (pnt != NULL && filename_cmp (pnt, ".obj") == 0)
+			if (pnt != NULL && fileext_cmp (pnt + 1, "obj") == 0)
 			  continue;
 
 			if (filename_cmp (bfd_get_filename (is3->the_bfd),
@@ -1701,7 +1718,7 @@ gld${EMULATION_NAME}_after_open (void)
 	       then leave the filename alone.  */
 	    pnt = strrchr (bfd_get_filename (is->the_bfd), '.');
 
-	    if (is_ms_arch && (filename_cmp (pnt, ".dll") == 0))
+	    if (is_ms_arch && pnt != NULL && (fileext_cmp (pnt + 1, "dll") == 0))
 	      {
 		int idata2 = 0, reloc_count=0;
 		asection *sec;
@@ -1855,9 +1872,9 @@ static bool
 gld${EMULATION_NAME}_unrecognized_file (lang_input_statement_type *entry ATTRIBUTE_UNUSED)
 {
 #ifdef DLL_SUPPORT
-  const char *ext = entry->filename + strlen (entry->filename) - 4;
+  const char *ext = strrchr (entry->filename, '.');
 
-  if (filename_cmp (ext, ".def") == 0 || filename_cmp (ext, ".DEF") == 0)
+  if (ext != NULL && fileext_cmp (ext + 1, "def") == 0)
     {
       pe_def_file = def_file_parse (entry->filename, pe_def_file);
 
diff --git a/ld/emultempl/pep.em b/ld/emultempl/pep.em
index ee36a9a7e56..accefc0ed60 100644
--- a/ld/emultempl/pep.em
+++ b/ld/emultempl/pep.em
@@ -181,6 +181,23 @@ static int is_underscoring (void)
   return pep_leading_underscore;
 }
 
+/* A case insensitive comparison, regardless of the host platform, used for
+   comparing file extensions.  */
+static int
+fileext_cmp (const char *s1, const char *s2)
+{
+  for (;;)
+    {
+      int c1 = TOLOWER (*s1++);
+      int c2 = *s2++; /* Assumed to be lower case from the caller.  */
+
+      if (c1 != c2)
+        return (c1 - c2);
+
+      if (c1 == '\0')
+        return 0;
+    }
+}
 
 static void
 gld${EMULATION_NAME}_before_parse (void)
@@ -1630,7 +1647,7 @@ gld${EMULATION_NAME}_after_open (void)
 		       extension, and use that for the remainder of the
 		       comparisons.  */
 		    pnt = strrchr (bfd_get_filename (is3->the_bfd), '.');
-		    if (pnt != NULL && filename_cmp (pnt, ".dll") == 0)
+		    if (pnt != NULL && fileext_cmp (pnt + 1, "dll") == 0)
 		      break;
 		  }
 
@@ -1647,7 +1664,7 @@ gld${EMULATION_NAME}_after_open (void)
 			/* Skip static members, ie anything with a .obj
 			   extension.  */
 			pnt = strrchr (bfd_get_filename (is2->the_bfd), '.');
-			if (pnt != NULL && filename_cmp (pnt, ".obj") == 0)
+			if (pnt != NULL && fileext_cmp (pnt + 1, "obj") == 0)
 			  continue;
 
 			if (filename_cmp (bfd_get_filename (is3->the_bfd),
@@ -1665,7 +1682,7 @@ gld${EMULATION_NAME}_after_open (void)
 	       then leave the filename alone.  */
 	    pnt = strrchr (bfd_get_filename (is->the_bfd), '.');
 
-	    if (is_ms_arch && (filename_cmp (pnt, ".dll") == 0))
+	    if (is_ms_arch && pnt != NULL && (fileext_cmp (pnt + 1, "dll") == 0))
 	      {
 		int idata2 = 0, reloc_count=0;
 		asection *sec;
@@ -1725,9 +1742,9 @@ static bool
 gld${EMULATION_NAME}_unrecognized_file (lang_input_statement_type *entry ATTRIBUTE_UNUSED)
 {
 #ifdef DLL_SUPPORT
-  const char *ext = entry->filename + strlen (entry->filename) - 4;
+  const char *ext = strrchr (entry->filename, '.');
 
-  if (filename_cmp (ext, ".def") == 0 || filename_cmp (ext, ".DEF") == 0)
+  if (ext != NULL && fileext_cmp (ext + 1, "def") == 0)
     {
       pep_def_file = def_file_parse (entry->filename, pep_def_file);
 
-- 
2.25.1